alimentary overview

levator labii superioris

to elevate the upper lip and draw it to one side

1. buccal cavity

2. palatine raphe

3. transverse ridges

4. soft palate

5. median sulcus

6. vestibule

1. vestibule

2. canine tooth

2a. philtrum

3. hard palate

4. soft palate

5. tongue

6. sublingual caruncle

7. palatoglossal arch

8. palatine tonsil

9. frenulum

serous gland

mucous gland

mixed gland

thyroarytenoideus- what does it give rise to

gives rise to ventricularis and vocalis muscles

vocalis

controls vocal cords

cricoarytenoideus dorsalis

abducts the arytendoidal cartilage to open the glottis

ventricularis

vocal fold adduction and glottis constriction

innervation to the larynx

cranial and caudal laryngeal nerves which originate from the vagus nerve

in equine gastric ulcer syndrome why are particular regions of the stomach affected

non glandular area lacks the protective mucus layer

what does this show

thick corrugated mucosa- cobblestone gut

johnes disease

what does this show

shortening and widening of villi which are infiltrated by large numbers ofmacrophages

viral antigen

what pathology can be seen here

red brown discolouration of mucosa

parvo

destruction of intestinal crypts and collapse of mucus

parvo

what is the stellate epithelium

star shaped epithelial cells in the enamel organ during development

nerve and blood supply of the tooth

Nerve & blood supply: superior and inferior alveolar (arteries, nerves & veins) In dental (pulp) cavity. At least one branch in each major elevation of the crow

digastrcus

wat type of epithelium covers the hard palate

keratinised stratified squamous

what type of epithelium coves the oral surface of the soft palate

stratified squamous

what glands are present in the soft palate

palatine

what type of epithelium covers the aboral surface of the soft palate

ciliated pseudostratified columnar

what kind of papillae

circumvallate

what kind of papillae

foliate

what epithelium lines the interlbular ducts

cuboidl to columnar epithelium

what gland is this and why

foamy appearance of the mucous cells is evident and the darker staining serous cells can be seen around the outside of the acini

mucous

serous

cells are typically cuboidal, pyramidal or crescent shaped

nuclei are psherical and cytoplasm stains well

what are reticular fibres composed of

type iii collagen plus proteoglycans and glyctoproteins

is there a lamina muscularis in the gallbladder

no

development of the gut tube

1. endoderm folds and elevates. splachnic mesoderm comes from the LPM

2. endoderm fold around ventrally. endoderm fuses ventrally

what is the primitive gut tube divided into

• foregut

• mid gut

• hind gut

which membrane is in the oral and anal region

oral- buccopharyngeal

anal- cloacal

layers of the gut- what do endoderm and splanphic mesoderm form

endoderm- epithelial cell adjacent to lumen

splanchnic mesoderm- connective tissue, smooth muscle and mesothelial layers (mesentery and peritoneum)

failure to perforate membranes

• persistent buccopharyngeal membrane in human- feeding is impossible, can perforate to treat

• persistent cloacal membrane in cow, must be perforated

foregut

• forms oesophagus, stomach, liver, gallbladder, bile ducts, pancreas, proximal duodenum

• must rotate and twist to elaborate into these structures

rotation of the foregut

what does the greater and lesser omentum contain

what can developmental defects of the omentum causse

• greater omentum contains gastrophrenic, gastrocolic, gastrosplenic ligaments

• lesser omentum contains hepatophrenic and hepatooesophageal ligaments

• developmental defects of the omentum can cause internal hernia

development of the spleen

• what type of cells does it form from and what is it also known as

• what is it in foetal stages

• forms from mesodermal cells in the dorsal mesentery- also called mesogastrium

• is a major haemopoetic tissue in foetal stages

what does the midgut consist of

• distal half of duodenum

• jejunum

• ileum

• cecum

• ascending colon

• proximal half of transverse colon

the equine caecum

• hindgut fermenter

• continues to grow in embryo

• in adults roughly 1m in length with a 30L capacity

species differences in ascending colon

• horse

• ruminant and pig

• horse- ascending colon continues to grow forming loop connected by remnants of dorsal mesentery

• ruminant and pig- ascending colon continues to grow forming spiral

rotation of the stomach

• what does it begin as

• what attaches it to the body walls

• what lies on the ventral and dorsal surfaces

• what happens first and what does it do the the other structures

• at the end what is the ventral and dorsal mesentery attachment

• begins as a spindle shaped tube

• ventral and dorsal mesenteries attach tube to body walls

• branches of the left and right vagus nerves lie on ventral and dorsal surfaces

• 90 degree clockwise rotation along the longitudinal axis then occurs

• this alters the course of the vagus nerve branches: right now innervates the ventral surface and left lies on the dorsal aspect

• as the stomach rotates along the ventral dorsal axis, the caudal end is displaced towards the right and cephalic end to the left

• ventral and dorsal mesenteries also displaced to right and left respectively

• lesser curvature is the ventral mesentery attachment

• greater curvature is the dorsal mesentery attachment

what does the ventral and dorsal mesentery give rise to

• ventral to falciform ligament which secures the liver ventrally

• also the lesser omentum which connects the liver and stomach and proximal duodenum

• dorsal mesentery gives rise to the greater omentum which is an apron like fold of mesentery that attaches to the greater curvature of the stomach and drapes over the small intestine

final arrangement of the biliary and pancreatic ducts step one

• what arise as outgrowths of the foregut

• what extend ventrally and dorsally

• what do liver buds outgrow into

• what happens to the proximal duodenum

1. abdominal accessory digestive organs arise as outgrowths of foregut prior to stomach and duodenal rotation

2. dorsal pancreatic duct extends dorsally

3. ventral pancreatic duct, gallbladder and liver buds extend ventrally

4. liver buds develoop as an outgrowth of the foregut into the septum transversum

5. proximal duodenum rotates clockwise

part 2

• what happens to the dorsal and ventral pancreatic buds and ducts

• then where does it go and exttnd

• what does the ventral pancreatic bud form

• where does the main and accessory pancreatic duct drain into and how

• what does the pancreatic duct join to and why

• how does the common bile duct form

• what direction does the common bile duct wrap around the duodenum

• what does it join with

• dorsal and ventral pancreatic buds and their ducts fuse

• the now formed complete pancreas nestles in the c curve of the duodenum and extends toward the left side of the body

• the uncinate process is the portion derived from the ventral pancreatic bud

• main pancreatic duct empties into the duodenum via major papilla

• accessory drains via minor

• the bile and pancreatic ducts join to drain bile and pancreatic juices at the major papilla

• liver drains bile into hepatic duct

• hepatic and cystic ducts merge to form the common bile duct

• due to the rotation of foregut and displacement of papillae the common bile duct wraps posteriorly around the duodenum

• it joins with the main pancreatic duct to drain bile at the major papilla to the duodenum

what are the four steps in midgut development

1. herniation and counterclockwise rotation: counterclockwise rotation about the axis of the superior mesenteric artery. midgut comprises the primary intestinal loop which elongates so rapidly that it temporarily outgrows the abdominal cavity, herniating into the umbilical cord

2. elongation: the caecum is now on the right hand side, as it has undergone a 270 degree rotation now (in pigs this is 450) . the rotated primary loop elongates rapidly creating the jejunoileal loops

3. retraction and counterclockwise rotation: loops retract from the umbilical cord into the abdominal cavity, and the intestines rotate 180 degrees counterclockwise as they continue to elongate. caecum now in upper right.

4. final positions: large intestine frames the small intestine. caecum now in the lower right

3 steps of hindgut development

• what closes off the cloaca

• what forms between the allantois and the hindgut

• what grows towards the cloacal membrane and what does it separate

• what happens to the cloacal membrane

• what separates the urogenital and anal membranes

1. cloaca: initially the cloaca is the common end of the hindgut and urogenital tract. the cloacal membrane (endoderm and ectoderm) close off the cloaca. the urorectal septum forms between the allantois and hindgut

2. urorectal septum: urorectal septum grows towards the cloacal membrane. it now separates the primitive urogenital sinus which appears as an anterior swelling. cloacal membrane ruptures before the urorectal septum reaches

3. perineal body: represents the tup of the urorectal septum, separates the urogenital and anal membranes. now completely divides the urinary and digestive tracts so that the urinary bladder lies anteriorly and anorectal canal remains posteirorly

tooth development from embryonic layers

• where does tooth development begin

• where are signals exchanged between and what does this initiate

• what happens and what structure is formed. what does this newly formed structure separate into

• what thickens

• what happens to the mesenchyme

• what forms

• …..

1. tooth development begins in the oral epithelium (ectodermal in origin.) signals exchanged between the oral epithelium and NCC derived mesenchyme underneath initiate odontogenesis

2. localised thickening of oral epithelium occurs forming the labiogingival band. this separates into the labiogingival lamina and the dental lamina.

3. thickening of dental laminae on medial aspect of the labiogingival band

4. mesenchyme underneath each laminae condenses

5. dental lamina invaginates forming the dental bud

6. dental bud expands and branches to form an enamel organ to surround a NCC derived dental papilla

7. this dental papilla enamel organ complex will form the deciduous tooth

8. a small mass of cells bud off from the dental lamina of the deciduous enamel organ, this cell cluster is the primordium of the permanent tooth.

what do the inner enamel epithelium differentiate into, how are odontoblasts derived, what does dentine and cementoblasts do?

• budding off of permanent tooth primordium continues

• inner enamel epithelium (derived from oral epithelium) differentiates into ameloblasts.

• cells in the dental papilla which are neural crest cell derived mesenchyme differentiate into odontoblasts.

• as odondoblasts lay down dentine, central part of the dental papilla remains as the pulp and the dentine surrounds the pulp and extends downwards to form tooth rot.

• later epithelial cells near distal part of tooth known as cementoblasts secrete cementum aorund tooth rot

ameloblasts

• what do they secrete

• how do they maintain contact with new unmineralised enamel

• what characteristic do they form

• what do they produce

• what happens after they erupt

secrete enamel which forms the outer covering of the tooth crown

maintain contact with new unmineralised enamel via cellular projections called thomes fibres

form crown characteristc of each tooth type

produce matrix which is not remodelled

are lost upon tooth eruption

odontoblasts- what do they do and what type of cell are they

secrete dentine which forms before enamel and induces enamel formation

columnar

role of mesenchyme, how are tooth tissues laid down

• mesenchymal cells can differentiate but have stable morphogenetic properties

• experimentally molar tooth mesenchyme and non oral ectoderm was combined resulting in a tooth shaped structure, showing that mesenchyme carries instructures for tooth morphology

• neural crest derived mesenchyme determines tooth type

• when molar mesenchyme is paired with incisor epithelium in culture the tooth that forms is a molar

• tooth tissues are laid down from the crown to the root

• tooth does not reach its final length while still embedded in jaw, achieved after eruption begins

tooth eruption- temporary

• eruption after crown is fully formed but before complete formation of the root

• eruption provides space for completion of root

• epithelial covering is continuous with gums upon eruption

• wear removed epithelium

permanent tooth eruption

• migrates into socket of temporary tooth

• increasing pressure from tooth

• resorption of temporary tooth root

• loosening

• shedding

• permanent tooth replaces

what aids tooth eruption?

• osteoclasts and odontoclasts resorb alveolar bone and root of the deciduous tooth to allow space for permanent tooth to move upward

• bone remodeling occurs to allow the tooth to move upward

• at the bottom of the developing root there is tissue fluid and blood supply which create hydrostatic pressure pushing the tooth upward as the root grows

• the periodontal ligament remodel collagen fibres and generate contractile forces to help pull the tooth upwards

Poll

dentine

• nature of production and rate

• contents

• produced continually

• rate increases during repair

• innervated

• mineralised matrix- collagen type i, dentine, specific protein

• odontoblasts recede from newly formed surfaces

• like bone but acellular

peridontal ligament

• where does it suspend tooth from

• what do the PDL fibres bridge

• shape

• what is it lined by

• suspends tooth in its alveolar socket

• fibres bridge alveolar bone and cementum

• shaped to accomodate tooth root-may be branched

• lined by compact bone

cementum

• what does it surround

• properties

• what collagen

• is it remodelled

• surrounds dentine of root

• mostly acellular

• not readily resorbed

• type i collagen

• not remodelled

can alveolar bone be remodelled

yes

what is the furcation angle

point where roots diverge in teeth with two or more roots

where does the crown meet the root

cemento enamel junction

what does the enamel consist of

hexagonal prisms or rods of hydroxyapatite crystals held together by cementing organic matrix

pulp

• connective tissue, nerves, lymph, blood vessels, collagen and undifferentiated reserve mesenchymal cells

what causes dentine to be sensitie to pain

Odontoblasts line the pulp cavity and branch into the dentine tubules. These branches, together with the fine nerve endings, cause the dentine to be sensitive to temperature and pain.

The odontoblasts lay down dentine and reduce the pulp cavity in size as the animal ages.